One of the product design principles is, we want the organic content to be of the same basic types of format as paid contact. Historically, advertisers want really rich things and we haven’t provided those. But one of the things we’ve provided in the last year, you see the organic News Feed posts move to richer mediums. A lot of that comes from immersive experiences like Instagram. When you have those form factors for content, that gives you the ability to offer those form factors for advertisements well.

Yahoo CEO Marissa Mayer has said multiple times that advertisements, if done well, can actually improve the user experience — and that’s something Facebook is keen on doing well, especially when it comes to mobile. Mobile revenue was about 23% of ad revenue for fourth quarter 2012, the company said in its last earnings announcement.

The core of that will, likely, come in the form of advertisements in the News Feed. For example, Facebook began rolling out app install advertisements, and already 20% of the top-grossing iOS apps are using it, Zuckerberg said on the call.

Now the next step is to add richer media to the equation — like big photos, big videos, and the ability to introduce some level of interactivity — to the News Feed that both users and advertisers can take advantage of when adding content.

The question will be whether that reduces user engagement, but so far that doesn’t seem to be a problem. Zuckerberg said the addition of advertising had barely affected user engagement, saying “the numbers turned out better than we expected… Now we have this News Feed ads business that we’ve barely tuned.”